Antivirals Reduce the Formation of Key Alzheimer's Disease Molecules in Cell Cultures Acutely Infected with Herpes Simplex Virus Type 1

Alzheimer's disease (AD) afflicts around 20 million people worldwide and so there is an urgent need for effective treatment. Our research showing that herpes simplex virus type 1 (HSV1) is a risk factor for AD for the brains of people who possess a specific genetic factor and that the virus causes accumulation of key AD proteins (β-amyloid (Aβ) and abnormally phosphorylated tau (P-tau)), suggests that anti-HSV1 antiviral agents might slow AD progression. However, currently available antiviral agents target HSV1 DNA replication and so might be successful in AD only if Aβ and P-tau accumulation depend on viral DNA replication. Therefore, we investigated firstly the stage(s) of the virus replication cycle required for Aβ and P-tau accumulation, and secondly whether antiviral agents prevent these changes using recombinant strains of HSV1 that progress only partly through the replication cycle and antiviral agents that inhibit HSV1 DNA replication. By quantitative immunocytochemistry we demonstrated that entry, fusion and uncoating of HSV1, are insufficient to induce Aβ and P-tau production. We showed also that none of the “immediate early” viral proteins is directly responsible, and that Aβ and P-tau are produced at a subsequent stage of the HSV1 replication cycle. Importantly, the anti-HSV1 antiviral agents acyclovir, penciclovir and foscarnet reduced Aβ and P-tau accumulation, as well as HSV1, with foscarnet being less effective in each case. P-tau accumulation was found to depend on HSV1 DNA replication, whereas Aβ accumulation was not. The antiviral-induced decrease in Aβ is attributable to the reduced number of new viruses, and hence the reduction in viral spread. Since antiviral agents reduce greatly Aβ and P-tau accumulation in HSV1-infected cells, they would be suitable for treating AD with great advantage unlike current AD therapies, only the virus, not the host cell, would be targeted

\u201cAmyloid-dependent triosephosphate isomerase nitrotyrosination induces glycation and tau fibrillation\u201d

Alzheimer's disease neuropathology is characterized by neuronal death, amyloid \u3b2-peptide deposits and neurofibrillary tangles composed of paired helical filaments of tau protein. Although crucial for our understanding of the pathogenesis of Alzheimer's disease, the molecular mechanisms linking amyloid \u3b2-peptide and paired helical filaments remain unknown. Here, we show that amyloid \u3b2-peptide-induced nitro-oxidative damage promotes the nitrotyrosination of the glycolytic enzyme triosephosphate isomerase in human neuroblastoma cells. Consequently, nitro-triosephosphate isomerase was found to be present in brain slides from double transgenic mice overexpressing human amyloid precursor protein and presenilin 1, and in Alzheimer's disease patients. Higher levels of nitro-triosephosphate isomerase (P < 0.05) were detected, by Western blot, in immunoprecipitates from hippocampus (9 individuals) and frontal cortex (13 individuals) of Alzheimer's disease patients, compared with healthy subjects (4 and 9 individuals, respectively). Triosephosphate isomerase nitrotyrosination decreases the glycolytic flow. Moreover, during its isomerase activity, it triggers the production of the highly neurotoxic methylglyoxal (n = 4; P < 0.05). The bioinformatics simulation of the nitration of tyrosines 164 and 208, close to the catalytic centre, fits with a reduced isomerase activity. Human embryonic kidney (HEK) cells overexpressing double mutant triosephosphate isomerase (Tyr164 and 208 by Phe164 and 208) showed high methylglyoxal production. This finding correlates with the widespread glycation immunostaining in Alzheimer's disease cortex and hippocampus from double transgenic mice overexpressing amyloid precursor protein and presenilin 1. Furthermore, nitro-triosephosphate isomerase formed large \u3b2-sheet aggregates in vitro and in vivo, as demonstrated by turbidometric analysis and electron microscopy. Transmission electron microscopy (TEM) and atomic force microscopy studies have demonstrated that nitro-triosephosphate isomerase binds tau monomers and induces tau aggregation to form paired helical filaments, the characteristic intracellular hallmark of Alzheimer's disease brains. Our results link oxidative stress, the main etiopathogenic mechanism in sporadic Alzheimer's disease, via the production of peroxynitrite and nitrotyrosination of triosephosphate isomerase, to amyloid \u3b2-peptide-induced toxicity and tau pathology

Modification of y-secretase by nitrosative stress links neuronal ageing to sporadic Alzheimer's disease

Inherited familial Alzheimer's disease (AD) is characterized by small increases in the ratio of Aβ42 versus Aβ40 peptide which is thought to drive the amyloid plaque formation in the brain of these patients. Little is known however whether ageing, the major risk factor for sporadic AD, affects amyloid beta‐peptide (Aβ) generation as well. Here we demonstrate that the secretion of Aβ is enhanced in an in vitro model of neuronal ageing, correlating with an increase in γ‐secretase complex formation. Moreover we found that peroxynitrite (ONOO−), produced by the reaction of superoxide anion with nitric oxide, promoted the nitrotyrosination of presenilin 1 (PS1), the catalytic subunit of γ‐secretase. This was associated with an increased association of the two PS1 fragments, PS1‐CTF and PS1‐NTF, which constitute the active catalytic centre. Furthermore, we found that peroxynitrite shifted the production of Aβ towards Aβ42 and increased the Aβ42/Aβ40 ratio. Our work identifies nitrosative stress as a potential mechanistic link between ageing and AD.This work was made possible by grants from the Fund for Scientific Research, Flanders; the K.U.Leuven; the VIB, Methusalem (K.U.Leuven and the Flemisch government), the Foundation for Alzheimer Research (SAO/FRMA), the European Research council (BDS), NIH AG15379 (OB), Spanish Ministry of Science and Innovation SAF 2010‐14906, Consolider 2010‐00045 (CGD), Spanish Ministery of Health (Fondo de Investigación Sanitaria‐PI10/00587 and Red HERACLES RD06/0009); The European FEDER Fundings; and Fundació La Marató de TV3 (Catalonia; Spain; no. 100310). We would like to acknowledge the Banc de Teixits Neurologics de l' Hospital Clinic de Barcelona and the Unidad de Neuropatología y Banco de Cerebros of Fundación Hospital Alcorcón for providing the brain samples. BDS is the Arthur Bax and Anna Vanluffelen chair for AD. FG obtained a IEF fellowship of the Marie Curie Actions program in FP7 and a Beatriu de Pinos grant of the Generalitat de Catalunya, Spain. TW was supported by EMBO and DFG long‐term fellowship

Modification of y-secretase by nitrosative stress links neuronal ageing to sporadic Alzheimer's disease

Inherited familial Alzheimer's disease (AD) is characterized by small increases in the ratio of Aβ42 versus Aβ40 peptide which is thought to drive the amyloid plaque formation in the brain of these patients. Little is known however whether ageing, the major risk factor for sporadic AD, affects amyloid beta‐peptide (Aβ) generation as well. Here we demonstrate that the secretion of Aβ is enhanced in an in vitro model of neuronal ageing, correlating with an increase in γ‐secretase complex formation. Moreover we found that peroxynitrite (ONOO−), produced by the reaction of superoxide anion with nitric oxide, promoted the nitrotyrosination of presenilin 1 (PS1), the catalytic subunit of γ‐secretase. This was associated with an increased association of the two PS1 fragments, PS1‐CTF and PS1‐NTF, which constitute the active catalytic centre. Furthermore, we found that peroxynitrite shifted the production of Aβ towards Aβ42 and increased the Aβ42/Aβ40 ratio. Our work identifies nitrosative stress as a potential mechanistic link between ageing and AD.This work was made possible by grants from the Fund for Scientific Research, Flanders; the K.U.Leuven; the VIB, Methusalem (K.U.Leuven and the Flemisch government), the Foundation for Alzheimer Research (SAO/FRMA), the European Research council (BDS), NIH AG15379 (OB), Spanish Ministry of Science and Innovation SAF 2010‐14906, Consolider 2010‐00045 (CGD), Spanish Ministery of Health (Fondo de Investigación Sanitaria‐PI10/00587 and Red HERACLES RD06/0009); The European FEDER Fundings; and Fundació La Marató de TV3 (Catalonia; Spain; no. 100310). We would like to acknowledge the Banc de Teixits Neurologics de l' Hospital Clinic de Barcelona and the Unidad de Neuropatología y Banco de Cerebros of Fundación Hospital Alcorcón for providing the brain samples. BDS is the Arthur Bax and Anna Vanluffelen chair for AD. FG obtained a IEF fellowship of the Marie Curie Actions program in FP7 and a Beatriu de Pinos grant of the Generalitat de Catalunya, Spain. TW was supported by EMBO and DFG long‐term fellowship